Single bellows water-cooled vehicle capacitors

ABSTRACT

A fluid cooled vacuum capacitor in which only a single metal bellows is required. Coolant is directed down the hollow center of the main shaft to the device and returns in a counterflow direction in the space between the shaft-bearing sleeve subassembly and the internal surface of the bellows. A unique fluid sealing arrangement includes primary and secondary shaft seals of the chevron type with circumferential expander springs and a leakage relief path between seals. Shaft bearings are metal-to-metal type and are fluid lubricated.

United States Patent Inventor Joseph E. Oeschger [56] References CitedPalo Alto, Calif- UNITED STATES PATENTS APP]- Filed Dec. 31,19693,243,672 3/1966 Srmonds 317/243 Patented Mar. 23, 1971 PrimaryExaminer-Elliot Goldberg Assignee International Telephone and TelegraphAttrneys-C. Cornell Remsen, Jr., Walter J. Baum, Paul W.

Corporation Hemminger, Charles L. Johnson, Jr. and Thomas E. New York,N.Y. Kristofferson ABSTRACT: A fluid cooled vacuum capacitor in whichonly a SINGLE BELLOWS WATER'COOLED VEHICLE single metal bellows isrequired. Coolant is directed down the CAPAFITORS hollow center of themain shaft to the device and returns in a Clams 3 Drawmg Flgs'counterflow direction in the space between the shaft-bearing US. Cl317/243, sleeve subassembly and the internal surface of the bellows A317/245, 174/ unique fluid sealing arrangement includes primary andsecon- Int. Cl H01g 1/08 dary shaft seals of the chevron type withcircumferential ex- Field of Search 317/243, pander springs and aleakage relief path between seals. Shaft 244, 245; 174/ 1 5 bearings aremetal-to-metal type and are fluid lubricated.

22 4 a n 7 I 20 l 58 I l c f 56 46 5/5 36 re 4/ 26 44 45 59 W 5 7 :1113i 56 /4 6/ 9 4 5/ I2 I 62 I r I I 1 I 5 PATENTEU HAR23 l97| INVENTOR.

JDSA'PH E. OESCHGER. BY

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SKNGILE IEELLOWS WATER-COOLER VEHICLE QAI ACETOR BACKGROUND OF THEINVENTION 1. Field of the Invention The invention relates tomechanically actuated variable electrical parameter devices in vacuo,and more particularly to fluid cooled variable vacuum capacitors.

2. Description of the Prior Art In the prior art, vacuum capacitors havebeen widely used in radio frequency circuits. The advantage ofrelatively high voltage and power handling capability for a given platespacing and the large degree of freedom from the adverse effects ofenvironmental conditions have caused such capacitors to be constructedin a variety of sizes.

As in all fundamentally reactive devices, there are inevitable intervallosses from such causes as circulating radio frequency currents andseries resistance (for example). In high power applications, the use offluid cooling is frequently indicated in order that internally generatedheat may be removed more efficiently than is possible by ordinaryambient air coiling. The result is that a fluid cooled capacitor of agiven power dissipation rating is substantially smaller than itotherwise would be. In using the term fluid, it is to be understood thatgasses as well as liquids are included in the broadest sense. Ilowever,liquids have much higher specific heats than gases, so that they are byfar the more efficient coolants at comparable flow rates. Accordingly,in the prior art as well as in the present invention, liquid coolingwould normally be used unless very special reasons dictated the use ofcirculating gas as a coolant. The invention is adapted for the use ofgas for the cooling fluid however.

A prior art vacuum capacitor with fluid cooling is described in US. fat.No. 3,270,259. In that reference, two internal concentric axial metalbellows are used to contain the fluid in the space between, whereas theevacuated space is between the outside bellows and the envelope of thedevice. Such devices are inherently rather expensive and difficult toconstruct. Many vacuum tight joints are necessary, and bellows lifetends to be low. Moreover, alignment problems during final assembly aremore difficult and the double bellows design forces the use of arelatively small central shaft and bearings of small diameter. This inturn lowers the mechanical resonance frequency of the entire movablecapacitor plate end of the internal structure. The yield strengths ofshaft and bearing assemblies is also correspondingly low. Accordingly,the environmental performance, particularly in respect to shock andvibration, are relatively poor compared to many types of nonfluid cooledsingle bellows vacuum capacitors. Steps taken to strength the doublebellows unit by the use of stainless steel or other high strengthmaterials for bearing bodies and shafts increased costs and didcomparatively little to raise the resonant frequency of the cantileveredvariable plate assembly.

SUMMARY OF THE INVENTION The present invention deals directly with theaforementioned prior art disadvantages to produce a vacuum capacitorwhich is mechanically rugged, has a high frequency mechanical resonance,provides more effective fluid cooling than prior art vacuum capacitorsand is relatively economically fabricated. This is because the coolantflow is through the ho]- low interior of the shaft itself and backaround between the outside of the relatively massive bearing body andthe inside bellows surface. Primary and secondary chevron seals providedbetween the shaft and bearing body adjacent to the fixed end of thebellows afford a fluidtight seal with backup in the event of any degreeof failure (leakage) of the primary seal. A floating sleeve and internalflange arrangement sliding along the bearing body preserves the bellowsconcentricity and lateral rigidity. The bellows itself is actually intwo sections axially. The adjacent interior end of each bellows sectionis joined (vacuum tight) to a corresponding face of the flange, byheliarc welding for example. The flange (which is actually a washer ordisc-shaped piece of itself) then travels axially with bellowscompression and elongation, and the integral sleeve correspondinglyslides over the bearing body outside diameter; thus providing radial andthrust support for the bellows, and controlling the tendency for thebellows to "snake."

Heat from the movable capacitor plate assembly is conducted into thebellows and into the shaft since these are firmly fixed to the saidplates through relatively massive metalto-metal contacts. The movableplates are mounted in a relatively heavy base plate and associatedstructure, as a result, the adjacent point at which coolant passesthrough the shaft wall openings into the volume between the shaft andbellows is a particularly effective heat transfer point.

The specific manner in which the apparatus of the present invention isconstructed will be apparent from the detailed description hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERREDEMBODIMENT Although, as indicated, the present invention is applicableto a variety of devices operating a vacua, this detailed descriptionwill be undertaken in respect to the invention used in a vacuumcapacitor.

Referring now to FIG. I, the invention will be seen to be illustratedalong with various structures which are of themselves prior art. Thecapacitor assembly is shown in section obtained by passing a planethrough the axial centerline of the device. It will be noted that asused in devices of this type the structure is essentially symmetricalabout the said axial centerline. A cylindrical ceramic body shell 1provides insulation between the end bell members 2 and 3 which are metalmembers and provide connection terminals for the capacitor. The ceramicbody shell is attached to the members 2 and 3 by means already known inthis art. That process and other vacuum capacitor fabrication techniquesapplicable to the overall structure are described in the literature,including U.S. Pat. application No. 820,451, filed Apr. 30, 1969, andassigned to the assignee of the present application.

From inspection, it will be apparent that members ll, 2, 3, 4, 48, Ill,28, 62, 45 3, 24 and the bellows sections h and 9 comprise the sealedstructure surrounding the evacuated volume. The said evacuated volumeincludes the contiguous spaces 52, 53, 5d and 55. Fixed capacitor plates5 and movable capacitor plates 6 are respectively mounted on the endplane 4 and the movable base plate 7. The capacitor plates 5 and 6typically are interleaving spirals or concentric cans" variouslydescribed in the prior art including those references referred to in theforegoing prior art discussion. Tubulations d5 and d6 provide forprocess steps including flushing of the plate assembly, introduction ofcleaning solutions and evacuation. It will be realized that any fluidintroduced during processing into 45 tends to fill the entire volume tobe evacuated and in doing so passes through the labyrinthine passagespresented by the interleaved capacitor plates, on its way to the othertubulation to. Both 45 and 46 are sealed after all processing stepsincluding evacuation have been completed, as one of the very last stepsin the manufacture of such vacuum capacitors. The bellows section 9 hasa formed closed end illustrated at M which is in good thermal contactwith the removable base plate 7. A space 57 is in communication with thecoolant through a passage 58 in the member 56.

Furnace brazing operations can be employed to perfect joints among thebellows 8, annular end plate 28, tubular body member ill, closure member4-3, end bell 3, ceramic body I, end bell 2 and closure plate 4. Thesetechniques are described in the technical literature, including theaforementioned US. Pat. application 820,45 1 filed Apr. 30, i969.

Lateral alignment of the base plane 7 and its rigidity against lateralvibration are important matters design and constructionwise, in thesubject device. Structural members associated with the annular end plate28 provide a rigid mounting for a tubular bearing body member 11. Ingeneral, in this description, the left end of the device as illustratedin FIG. 1 will be referred to as the control end since it is here thatmechanical thrust is applied which results in the interleaving orwithdrawing of the plate assemblies and 6. Fitted within the bearingbody it is the hollow shaft lid which has an axial bore or hollowinterior 2H. The clearance between the bearing body ll. and the shaftlid is substantially more than necessary to provide a sliding tit exceptwhere the bearing body inside diame ter is reduced at 26 and 27 to formbearing surfaces to support the shaft M at all times and to permit it totranslate axially in response to thrust applied to the end cap 18. Theend cap 18 is adapted to be activated axially by means of a linkageengaging the shear pin opening 39, for example. The activating forcethus moves the entire end cap 18 and the shaft M which are joined bythread mating (for example) to 3%. Setscrew 40 secures these partsagainst possible unscrewing.

Since the novel structure described includes a unique and much improvedfluid cooling arrangement, the structure relating to this coolingfunction and the resultant fluid paths will next be described. At theoutset, however, it is noted that although the term fluid is used togenerally described the range of coolants useable in this device toinclude liquids and gases, by far the most common coolant used indevices of this type is water or a liquid solution which is mostly waterwith a few corrosion inhibiting additives, etc. The two main liquidconnections are shown at 19 and 31 and although either could beconsidered the inlet or outlet, it was desirable in a particularembodiment of this invention to introduce the liquid coolant at 19 andpermit it to exit at 31. This is because liquid flow in this directionreaches the vicinity of the bellows end 44 cooler than if it had reachedthe same point in the reverse flow direction. Accordingly thetemperature gradient between the coolant and the heat conducting partsin the vicinity of 44 was larger and the heat transfer correspondinglygreater.

Since the entire end cap iii is movable in response to the activatingforce, it will be evident that a flexible connection at 19 is required.Liquid entering at 19 first reaches the space 20 within 18 and proceedsdown the hollow internal volume 21 of the shaft 114. As illustrated inFIG. ll, there are at least two lateral passageways, typically 22, whichpass coolant readily through the shaft assembly wall at these points.The number of passages 22 existing radially about the circular crosssection of the shaft assembly in this location is a matter of design,considering that the bellows header is cooled mostly at this point. Theplate 56 is a substantial recipient of conducted heat from 7 (and otherparts adjacent to the capacitor plates). Coolant passing through thepassages 22 will be seen to return toward the control end of the devicein the volume 23 between shaft M and bellows section 9. The bellowsheader 441, being dimpled in the center, acts as an alignment spindlefor movable plate assembly, and the cavity created at 57 is opened tothe fluid by passage 53.

As an added feature of the novel structure it will be noted that the twobellows sections 8 and 9 are joined to an annular disc or washer shapedmember 12 which in turn joined to a sleeve 113. Since the joining of thetwo bellows sections to 12 requires a vacuumtight seal, prefabricationof these parts before final assembly requires vacuumtight joining ofbellows sections 8 and 9 to 12. For this purpose, two circumferentialheliarc weld beads 25 are deposited. The clearance between the sleeve 13and the bearing body ii is just sufficient to permit 33 to slide easilyover 11 in this liquid lubricant environment. A plurality of axialpassages 24 through the member 112 provide for the flow of coolantliquid from the space 23 through to the space 5@ and along parallel tothe bearing body ill. The bearing body shoulder 60 is provided withslots in its circumferential contact surface with 28. The coolant liquidflowing through space 59 is able to proceed into a liquid plenum space32 through these slots 30. A plenum end bell 29 joined with 28, and withbearing body ll adjacent to the end flange 50 as illustrated, providesthe enclosure of the said liquid plenum 32. Members 29 and 50 arepreferably brazed together at 5!. The exit liquid connection 32communicates directly with the plenum space 32. Bellows 1E3, anchored tothe end cap 18 by a spring clamp to, acts merely as a dust cover and isnot required to resist the liquid pressure. The said liquid pressure iscontained by a novel double sliding seal arrangement comprising seals 3dand 35 to be described in more detail hereinafter.

The O-ring seal i7 acts merely as a fixed gasket since there is norelative motion between 14 and iii. A clamp plate d9, screwed to the endflange 5i serves to anchor the bellows E5 to the nonmoving structure ofthe device. As indicated previously, the bearing surfaces 26 and 2'7 andthe sliding surfaces between 13 and 11 are liquid lubricated andopenings typically shown at l -'7' through the bearing body wall areprovided to encourage some fluid circulation in the space between M andll. Since the bearing surface 27 is liquid lubricated in sliding, a sealbetween the shaft and bearing body is a practical functional necessity.The said unique seal consists to two teflon (or like fluorocarbonchevron seals, each with expander spring 61 in a circumferential groovein the pressure receiving face thereof. A perforated spacer ring, as forexample as shown at 36, provides a leakage receiving volume between thetwo seals. FIG. 2 shows these seals 3d and 35 and the spacer ring 36 inexploded view of their functional relationship for a betterunderstanding of their exact configuration. The actual leadage spaceprovided around spacer 36 communicates with a radial passage 13 in thelarge diameter body of 11 and from there to an external connection 33.The seal 34 may be thought of as being the primary seal at this point ofrelative motion between 11 and 14. Seal 35 may be thought of as a backup, or secondary seal and is retained in a counterbore in the large endof the bearing body 11 by an expansion ring 38 seated in a correspondinggroove in the said counterbore. A washer 37 holds the seal 35 in place.The actual shape of the counterbore can be utilized to hold the seal 34in place axially at the opposite end of the seal assembly.

Relief passages 41 and 42 (typical) provide relief from possibleentrapment of wear products in the space against the spring face of seal34. FIG. 2 also shows the nature of the circumferential expander springs61 which operate to preserve the chevron shape of these seals forbearing against the shaft outside and bearing body inside surfaces.

Appropriate materials for the various parts of the complete structurenot specifically indicated in this description are well known in thisart. The novel structure is obviously adapted for inclusion in glassbody versions of the apparatus described.

Various modifications and variations within the intended scope of thepresent invention will suggest themselves to those skilled in the art,once the inventive concepts are understood. Accordingly, it is notintended that this description or the drawings hereof are to beconsidered as limiting the scope of this invention.

lclaim: i. In a device utilizing an extendable metal bellows protrudingfrom an exterior end into an evacuated envelope for providing mechanicalmotion within said evacuated envelope to a heat dissipating device, saidmechanical motion being provided by a shaft through the interior of saidbellows to apply motive force to the interior end of said bellows, thecombination comprising:

means including an axial bore within said shaft and at least one radialfluid pamage through the wall of said shaft adjacent to said bellowsinterior end, to permit return fluid flow in the volume between saidshaft and said bellows;

fluid seal means for sealing the volume between said bellows and saidshaft against fluid leakage while permitting at least thrust motion ofsaid shaft with respect to said exterior bellows end;

and means for providing fluid connections to the exterior end of saidshaft bore and to said volume between said shaft and said bellowssubstantially at said exterior end, thereby to establish a circuit forflow of coolant fluid.

2. A vacuum capacitor assembly including fixed plates located adjacentone end within a vacuumtight housing of substantially circular crosssection, movable plates arranged to be interleaved and withdrawn withrespect to said fixed plates in response to axial movement of asubstantially concentric shaft within said housing mechanicallyconnected to said movable plates, and an extendable metal bellows vacuumsealed to said shaft at one end adjacent said movable plates and to saidhousing at the control end, whereby the evacuated volume surrounds saidplates and extends between said bellows and said envelope, thecombination comprising:

a tubular bearing body mechanically supported from said control end andextending cantilevered within said bellows, said bearing having at leasta portion of its inside diameter sufficiently small over at least twoaxial increments to form interior bearing surfaces for said shaft.

means including an axial bore in said shaft for conducting cooling fluidaxially through said shaft toward said plates;

means comprising at least one radial opening through said shaft walladjacent said movable plate vacuum seal, whereby said cooling fluidpasses into the space between said bellows and the outside perimeter ofsaid bearing body;

means comprising a fluid plenum surrounding the perimeter of saidbearing at said control end;

passage means comprising at least one generally axial opening through aportion of said bearing body at said control end so as to allow fluidpassage from the space between said bellows and said bearing bodyoutside perimeter into said plenum;

means comprising a substantially fluidtight ring shape seal between saidshaft and the inside surface of said bearing body, said seal beingadapted to permit sliding of said shaft within said bearing body whilemaintaining said fluidtight characteristic of said ring seal.

3. The invention defined in claim 2, further defined in that saidbearing body comprises an axial section of enlarged outside diameterthereby forming a shoulder which acts as an end plate at the control endof said bellows, said bearing body is counterbored from said control endat the location of said ring seal, thereby to provide an annularreceptacle for said bearing,

and said passage means is through said shoulder.

4. The invention set forth in claim 3, further defined in that said ringseal includes at least one fluorocarbon ring of the type having anelongated helical wire spring inserted in a circumferential groove inthe face of said ring facing the direction of fluid pressure.

5. The invention set forth in claim 3 in which said seal comprisesprimary and secondary seals separated by a nonsealing spacer, andadditional means are provided for externally venting the volume betweensaid seals, thereby to provide a backup for said primary seal andexternal relief for and evidence of leakage around said primary seal.

6. The invention set forth in claim 2, further defined in that saidbearing body includes at least one radial opening in the wall of saidbearing body thereby to provide a fluid path between said volume betweensaid bellows and said outside perimeter of said bearing body and theradial clearance between said shaft and said bearing body and said shaftalong the axial distance between saidbearing surfaces, thereby toprovide at least some fluid circulation adjacent to said shaft and toenhance the fluid lubrication of said bearing surfaces.

7. The invention set forth in claim 2, further defined in that saidbellows is divided into a plurality of axial sections, said sections arebutt joined'in a vacuumtight manner to a washer having an outsidediameter comparable to the outside diameter of said bellows and aninside diameter joined to a sleeve having an inside diameter whichfreely fits over the outside diameter of said bearing body, thereby toprovide lateral stiffness for said bellows.

8. The invention set forth in claim 7 further defined in that saidwasher includes at least one axial fluid passage enhancing fluid flowbetween said bearing body and said bellows.

9, The invention set forth in claim 3, further defined in that saidbearing body includes at least one fluid relief passage between saidcounter bore on the pressurized sideof said primary seal and said volumebetween said bellows and said bearing body.

10. The invention set forth in claim 5 further defined in that saidmeans for externally venting said volume between said chevron sealscomprises a passage which is fluidtight with respect to said plenum andpasses through said plenum and its external wall thereby to provide saidexternal venting,

1. In a device utilizing an extendable metal bellows protruding from anexterior end into an evacuated envelope for providing mechanical motionwithin said evacuated envelope to a heat dissipating device, saidmechanical motion being provided by a shaft through the interior of saidbellows to apply motive force to the interior end of said bellows, thecombination comprising: means including an axial bore within said shaftand at least one radial fluid passage through the wall of said shaftadjacent to said bellows interior end, to permit return fluid flow inthe volume between said shaft and said bellows; fluid seal means forsealing the volume between said bellows and said shaft against fluidleakage while permitting at least thrust motion of said shaft withrespect to said exterior bellows end; and means for providing fluidconnections to the exterior end of said shaft bore and to said volumebetween said shaft and said bellows substantially at said exterior end,thereby to establish a circuit for flow of coolant fluid.
 2. A vacuumcapacitor assembly including fixed plates located adjacent one endwithin a vacuumtight housing of substantially circular cross section,movable plates arranged to be interleaved and withdrawn with respect tosaid fixed plates in response to axial movement of a substantiallyconcentric shaft within said housing mechanically connected to saidmovable plates, and an extendable metal bellows vacuum sealed to saidshaft at one end adjacent said movable plates and to said housing at thecontrol end, whereby the evacuated volume surrounds said plates andextends between said bellows and said envelope, the combinationcomprising: a tubular bearing body mechanically supported from saidcontrol end and extending cantilevered within said bellows, said bearinghaving at least a portion of its inside diameter sufficiently small overat least two axial increments to form interior bearing surfaces for saidshaft. means including an axial bore in said shaft for conductingcooling fluid axially through said shaft toward said plates; meanscomprising at least one radial opening through said shaft wall adjacentsaid movable plate vacuum seal, whereby said cooling fluid passes intothe space between said bellows and the outside perimeter of said bearingbody; means comprising a fluid plenum surrounding the perimeter of saidbearing at said control end; passage means comprising at least onegenerally axial opening through a portion of said bearing body at saidcontrol end so as to allow fluid passage from the space between saidbellows and said bearing body outside perimeter into said plenum; meanscomprising a substantially fluidtight ring shape seal between said shaftand the inside surface of said bearing body, said seal being adapted topeRmit sliding of said shaft within said bearing body while maintainingsaid fluidtight characteristic of said ring seal.
 3. The inventiondefined in claim 2, further defined in that said bearing body comprisesan axial section of enlarged outside diameter thereby forming a shoulderwhich acts as an end plate at the control end of said bellows, saidbearing body is counterbored from said control end at the location ofsaid ring seal, thereby to provide an annular receptacle for saidbearing, and said passage means is through said shoulder.
 4. Theinvention set forth in claim 3, further defined in that said ring sealincludes at least one fluorocarbon ring of the type having an elongatedhelical wire spring inserted in a circumferential groove in the face ofsaid ring facing the direction of fluid pressure.
 5. The invention setforth in claim 3 in which said seal comprises primary and secondaryseals separated by a nonsealing spacer, and additional means areprovided for externally venting the volume between said seals, therebyto provide a backup for said primary seal and external relief for andevidence of leakage around said primary seal.
 6. The invention set forthin claim 2, further defined in that said bearing body includes at leastone radial opening in the wall of said bearing body thereby to provide afluid path between said volume between said bellows and said outsideperimeter of said bearing body and the radial clearance between saidshaft and said bearing body and said shaft along the axial distancebetween said bearing surfaces, thereby to provide at least some fluidcirculation adjacent to said shaft and to enhance the fluid lubricationof said bearing surfaces.
 7. The invention set forth in claim 2, furtherdefined in that said bellows is divided into a plurality of axialsections, said sections are butt joined in a vacuumtight manner to awasher having an outside diameter comparable to the outside diameter ofsaid bellows and an inside diameter joined to a sleeve having an insidediameter which freely fits over the outside diameter of said bearingbody, thereby to provide lateral stiffness for said bellows.
 8. Theinvention set forth in claim 7 further defined in that said washerincludes at least one axial fluid passage enhancing fluid flow betweensaid bearing body and said bellows.
 9. The invention set forth in claim3, further defined in that said bearing body includes at least one fluidrelief passage between said counter bore on the pressurized side of saidprimary seal and said volume between said bellows and said bearing body.10. The invention set forth in claim 5 further defined in that saidmeans for externally venting said volume between said chevron sealscomprises a passage which is fluidtight with respect to said plenum andpasses through said plenum and its external wall thereby to provide saidexternal venting.